The present invention relates to a dent removal arrangement, and more particularly, to an arrangement for smoothing and shrinking dented plates or the like by way of an electrode, fitted to a handle in the manner of a hammer, connected to one pole of a voltage source, the other pole of which is connected to the plate to be worked, with the electrode being surrounded by a coaxially disposed cylindrical shield or anti-dazzle device.
A dent removal device of the electrode-type has been described, for example, in German Offenlegungsschrift No. 2 362 103 , wherein electrical joulean heat is employed for a brief local heating of the sections or parts of the plate to be worked or re-shaped. Generally, in the reworking of a dented plate, the indentations are first pressed out with a conventional dent removal tool and then the uneven parts which still remain are subjected to a grinding operation to clean the same, thereby improving the electrical conductivity of the plate. The thus processed dented plate is then connected to one pole of a voltage source, for example, a welding transformer with an output of approximately 50 volts, with the other pole of the voltage source being connected to the electrode-type dent removal device. Upon a touching of the dented plate with the electrode, the circuit is closed and the plate is strongly heated for a split second during the contact period. During a subsequent cooling period, the plate is re-shaped to conform to its initial state. By repeatedly touching the plate with the electrode or by sliding the electrode over the plate, the dented plate can gradually be re-shaped to the smooth surface of its initial state.
One advantage of the electrode-type dent removal arrangement over a dent removal by way of an oxy-acetylene welding arrangement resides in the fact that, in the former arrangement, only a brief local heating occurs. Therefore, inner linings, cable linings and the like disposed in proximity to or protected by the plate being worked or re-shaped are protected from damage resulting from an overall heating of the plate. Consequently, the linings, cable lines and the like need not be removed during the repair of the dented plate.
A further advantage of the electrode-type dent removal arrangement resides in the fact that the plate sections or parts being treated are fairly free from stresses after working, so that the stability of the repaired plate part is maintained.
One disadvantage of the conventional electrode-type dent removal arrangement of the afore-mentioned type resides in the fact that, in the repair of large or difficult plate areas, it is necessary to include in the dent removing process cooling pauses throughout because it is necessary first to wait for the plate to re-shape gradually during cooling to ascertain the respective state of the reformation and, second, without a cooling pause, the neighboring parts such as the inner linings, cables and the like, gradually become hot, thereby subjecting these parts to possible damage. Furthermore, the quality of the dent removal process falls significantly with increasing temperatures.
It has been proposed to reduce the working voltage and/or current to thereby delay the gradual heating of the plate; however, such proposals have only had partial success since such proposals result in the overall dent-removing process time increasing disproportionately. Therefore, in the conventional electrode-type dent removal arrangements, it may be necessary to wipe the heated plate parts or sections from time to time with, for example, a wet cloth or the like.
The aim underlying the present invention essentially resides in providing an arrangement for smoothing and shrinking dented elements, whereby the plate re-working process may be carried out most conveniently by providing a cooling of the surrounding plate parts simultaneously with the touching or contacting of the electrodes and the plate, and also by the local heating of an uneven area. By virtue of such an arrangement, the working progress attained is immediately fixed and smoothing can readily be continued without any interruption in the work, since the operating personnel are able to ascertain the effect of the plate smoothing practically immediately after each touching or stroking of the plate with the electrode.
According to the present invention, an electrode-type arrangement for smoothing and shrinking a dented plate is provided with the electrode being fitted to a handle in the manner of a hammer, and with the electrode being connectable to one pole of a voltage source, the other pole of which is connectable to the plate to be worked. Furthermore, the electrode is surrounded by a coaxial disposed, preferably, a cylindrical shield or anti-dazzle device which may be combined with a cooling element for at least cooling the region of the plate part to be worked.
One advantage of combining the electrode with the cooling element resides in the fact that the electrode material is heated to a lesser extent and is, therefore, subjected to less wear. Also, a better surface quality of the worked surface part is obtainable.
According to one advantageous feature of the present invention, the shield or anti-dazzle device is in the form of a cylindrical container and functions simultaneously as a casing or housing for accommodating a cooling element.
According to one embodiment of the present invention, the cooling element itself is preferably an annular sponge held in an annular space provided between the electrode and the shield or anti-dazzle device, with the other end surface of the sponge being aligned with or projecting beyond the working surface of the electrode. By virtue of this construction, the dent removal device need only be dipped into water or other cooling fluid at the beginning of the working, so that the water or other fluid is absorbed into the sponge. Upon the touching or sliding of the electrode over the dented plate, the vicinity of the area on the plate contacted by the electrode is wetted with the cooling liquid so that even with a large working area, there is no unduly great heating of the entire plate.
According to another particularly advantageous feature of the invention, the sponge element may project beyond the electrode working surface so that the elastic resilience of the sponge allows only brief contact between the electrode and the plate being worked, while a good cooling of the neighboring zones is insured as the overlying sponge is, to some extent, squeezed and, therefore, makes sufficient cooling liquid available.
According to still yet another advantageous feature of the present invention, the shielding or anti-dazzle device is preferably made of an elastic material with the other edge thereof being approximately aligned with the electrode working surface. By virtue of this construction, no damage can occur during the touching or sliding of the electrode, and the shielding or anti-dazzle device lies firmly on the plate, thereby preventing unnecessary cooling liquid losses.
In a further embodiment of the present invention, the cooling is realized by providing a compressed air line which may open into an annular space between the electrode and the shield or anti-dazzle device. To enhance the cooling effect of a construction of this type, the compressed air may be fed through several holes distributed about the electrode in the immediate vicinity thereof. The presence of the shield or anti-dazzle device maintains the cooling air in the region of the electrode, so that even with small quantities of cooling air, a good cooling effect is nevertheless obtained.
In accordance with a further feature of the present invention, rather than supply compressed air, a cooling fluid such as, for example, water, may be directed into the annular space between the electrode and the shield. If desired, several holes may be distributed about the electrode in order to more effectively feed the cooling liquid to the immediate vicinity of the electrode.
Preferably, in accordance with the present invention, the electrode may be of the form of a replaceable copper cotton pin which is locked in a cylindrical support which is slightly set back. This construction is desirable since the shape of the plate indentations normally are considerably varied. By providing an electrode mounted in this manner, the operation can therefor be carried out with different electrode shapes and worn electrodes can be easily replaced. The support for the cotter pin forming the electrode may be provided with a flat end surface which also may function as an electrode if the cotter pin is removed.
Accordingly, it is an object of the present invention to provide an electrode-type dent removal arrangement which avoids, by simple means, the afore-mentioned shortcomings and drawbacks encountered in the prior art.
Another object of the present invention resides in providing an improved electrode-type dent removing arrangement which permits the re-working process of a dented plate to be continued without any interruption.
A further object of the present invention resides in providing an electrode-type dent arrangement, wherein the electrode material is subjected to less wear.
Still another object of the present invention resides in providing an improved electrode-type dent removing arrangement which permits a better surface quality of the worked surface part than obtainable by prior art constructions.
A still further object of the present invention resides in providing electrode-type dent removing arrangement which is combined with a cooling construction for cooling at least the region of the plate part to be worked.